tailieunhanh - Smog - A REPORT TO THE PEOPLE Episode 6

Tham khảo tài liệu 'smog - a report to the people episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | sources by requừing reductions in the stack concentrations as shown in Table 13. Several techniques have been used to achieve these reductions without affecting the boiler efficiency. One is multiple-stage combustion which achieves some reduction in the peak temperatures of the combustion flame. This reduction can be further augmented by flue-gas recirculation but recirculation is more difficult to retrofit to existing boilers. Another technique involves reducing the excess air so that combustion is closer to stoichiometric while carefully avoiding any increase in hydrocarbon or carbon monoxide emissions. Similar techniques could be applied to many other industrial boilers and heaters in use. The petroleum industry is the largest contributor. Most likely additional rules will be requứed so that Rule 68-type constraints are applied to these NOX producers. Industrial plants also use large internal combustion engines operating with process-produced fuel gas to supply mechanical power for pumping etc. These engines would respond to the same NOX control techniques used for automobiles such as exhaust gas recirculation manifold or catalytic exhaust reactors etc. to reduce their NOX emissions. However additional rules would be needed since these sources are not controlled by any of the present regulations. A feasible control program is outlined in quantitative terms in Table 14. The strategy involves achieving some reductions from each of several source types by one of the possible control techniques. Additional reductions of about 14 tons per day are possible in large boilers and small power plants by utilizing flue-gas recirculation as well as low excess air at an additional cost of about 14 million dollars. One problem facing the NOX reduction program is the difficulty in obtaining sufficient natural gas to meet the fuel requứements over the next few years. This shortage will necessitate burning oil with resultant higher NOX levels because of poorer combustion control.